Air conditioner unit and method for operating same

ABSTRACT

Air conditioner units and methods for operating air conditioner units are provided. A method includes determining an operational state of each heater bank of a plurality of heater banks of the air conditioner unit, and determining a speed of a blower fan of the air conditioner unit when the operational state of every heater bank is active. The method further includes comparing a blower fan input voltage to a voltage threshold value when the speed is a low speed, and deactivating one of the plurality of heater banks when the blower fan input voltage is less than the voltage threshold value.

FIELD OF THE INVENTION

The present disclosure relates generally to air conditioner units, andmore particularly to methods and apparatus for reducing or eliminatingoverheating of air conditioner units during heating operations.

BACKGROUND OF THE INVENTION

Air conditioner units are conventionally utilized to adjust thetemperature within structures such as dwellings and office buildings. Inparticular, one-unit type room air conditioner units may be utilized toadjust the temperature in, for example, a single room or group of roomsof a structure. A typical such air conditioner unit includes an indoorportion and an outdoor portion. The indoor portion is generally locatedindoors, and the outdoor portion is generally located outdoors.Accordingly, the air conditioner unit generally extends through a wall,window, etc. of the structure.

In the outdoor portion of a conventional air conditioner unit, acompressor that operates a refrigerating cycle is provided. At the backof the outdoor portion, an outdoor heat exchanger connected to thecompressor is disposed, and facing the outdoor heat exchanger, anoutdoor fan for cooling the outdoor heat exchanger is provided. At thefront of the indoor portion of a conventional air conditioner unit, anair inlet is provided, and above the air inlet, an air outlet isprovided. A blower fan and a heating unit are additionally provided inthe indoor portion. Between the blower fan and heating unit and the airinlet, an indoor heat exchanger connected to the compressor is provided.

When cooling operation starts, the compressor is driven to operate therefrigerating cycle, with the indoor heat exchanger serving as acold-side evaporator of the refrigerating cycle, and the outdoor heatexchanger as a hot-side condenser. The outdoor heat exchanger is cooledby the outdoor fan to dissipate heat. As the blower fan is driven, theair inside the room flows through the air inlet into the air passage,and the air has its temperature lowered by heat exchange with the indoorheat exchanger, and is then blown into the room through the air outlet.In this way, the room is cooled.

When heating operation starts, the heating unit is operated to raise thetemperature of air in the air passage. The air, having had itstemperature raised, is blown out through the air outlet into the room toheat the room.

In many currently known air conditioner units, the heating unit isformed from a plurality of heater banks. Each bank may have a differentrated power output. The highest output for the unit generally occurswhen all heater banks are operating at the same time. Additionally, manycurrently known air conditioner units have multiple blower fan speedsettings. For example, a blower fan may in some cases be operated at alow setting or a high setting, or in some cases at various otherintermediate settings.

One concern during operation of air conditioner units is overheating ofthe unit, particularly if a blockage occurs. For example, a blockage tothe air inlet path and/or air outlet path prevents proper airflow fromoccurring within the unit. Particularly when all heater banks are on andthe fan speed is low, temperatures within the unit can risesignificantly, leading to deformation and/or other damage to componentsof the unit. Particularly vulnerable components include, for example,plastic components of the heater housing.

Accordingly, improved methods and apparatus for operating airconditioner units are desired. In particular, methods and apparatus thatreduce or prevent overheating of the air conditioner unit would beadvantageous.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In accordance with one embodiment, a method for operating an airconditioner unit is provided. The method includes determining anoperational state of each heater bank of a plurality of heater banks ofthe air conditioner unit, and determining a speed of a blower fan of theair conditioner unit when the operational state of every heater bank isactive. The method further includes comparing a blower fan input voltageto a voltage threshold value when the speed is a low speed, anddeactivating one of the plurality of heater banks when the blower faninput voltage is less than the voltage threshold value.

In accordance with another embodiment, an air conditioner unit isprovided. The air conditioner unit includes a blower fan, the blower fancomprising a blade assembly and a motor connected to the blade assembly.The air conditioner unit further includes a heating unit, the heatingunit comprising a plurality of heater banks. The air conditioner unitfurther includes a power source in electrical communication with theblower fan motor and the plurality of heater banks, and a controller inoperable communication with the motor and the plurality of heater banks.The controller is operable for determining an operational state of eachheater bank, determining a speed of the blower fan when the operationalstate of every heater bank is active, comparing a blower fan inputvoltage to a voltage threshold value when the speed is a low speed, anddeactivating one of the plurality of heater banks when the blower faninput voltage is less than the voltage threshold value.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 provides a perspective view of an air conditioner unit, with aroom front exploded from a remainder of the air conditioner unit forillustrative purposes, in accordance with one embodiment of the presentdisclosure;

FIG. 2 is a perspective view of components of an indoor portion of anair conditioner unit in accordance with one embodiment of the presentdisclosure;

FIG. 3 is a schematic diagram of components of an air conditioner unitin accordance with one embodiment of the present disclosure; and

FIG. 4 is a flow chart illustrating steps of a method in accordance withone embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

Referring now to FIG. 1, an air conditioner unit 10 is provided. The airconditioner unit 10 is a one-unit type air conditioner, alsoconventionally referred to as a room air conditioner. The unit 10includes an indoor portion 12 and an outdoor portion 14, and generallydefines a vertical direction V, a lateral direction L, and a transversedirection T. Each direction V, L, T is perpendicular to each other, suchthat an orthogonal coordinate system is generally defined.

A housing 20 of the unit 10 may contain various other components of theunit 10. Housing 10 may include, for example, a rear grill 22 and a roomfront 24 which may be spaced apart along the transverse direction by awall sleeve 26. The rear grill 22 may be part of the outdoor portion 14,which the room front 24 is part of the indoor portion 12. Components ofthe outdoor portion 14, such as an outdoor heat exchanger 30, outdoorfan (not shown), and compressor (not shown) may be housed within thewall sleeve 26. A casing 34 may additionally enclose the outdoor fan, asshown.

Referring now also to FIGS. 2 and 3, indoor portion 12 may include, forexample, an indoor heat exchanger 40, a blower fan 42, and a heatingunit 44. These components may, for example, be housed behind the roomfront 24. Additionally, a heater housing 46 may generally support and/orhouse various other components or portions thereof of the indoor portion12, such as the blower fan 42 and the heating unit 44.

Heater housing 46 may have peripheral surfaces 50 that define a housinginterior 51. For example, the peripheral surfaces 50 may include a firstsidewall 52 and a second sidewall 54 which are spaced apart along thelateral direction L. Peripheral surfaces 50 may additionally include abase pan 56 and an outlet air diverter 58, each of which may extendbetween the sidewalls 52, 54 along the lateral direction L.

The housing 46 may be formed from one or more components. For example,in exemplary embodiments, the housing 46 may be formed from a bulkhead60 and a shroud 62. The bulkhead 60 may in some embodiments be formedfrom a suitable plastic, or alternatively may be formed from anysuitable material. The shroud 62 may in some embodiments be formed froma suitable metal, or alternatively may be formed from any suitablematerial. The shroud 62 may be connected to the bulkhead 60, and thebulkhead 60 and shroud 62 may together include the peripheral surfaces50. For example, base pan 56 and outlet air diverter 58 may becomponents of the bulkhead 60, and portions of or entire sidewalls 52,54 may be components of the shroud 62. Shroud 62 may additionallyinclude an interior shroud base 64, which may for example be disposedwithin interior 51 adjacent base pan 56.

In exemplary embodiments, blower fan 42 may be a tangential fan.Alternatively, however, any suitable fan type may be utilized. Blowerfan 42 may include a blade assembly 70 and a motor 72. The bladeassembly 70, which may include one or more blades disposed within a fanhousing 74, may be disposed within the interior 51 of the heater housing46. As shown, blade assembly 70 may for example extend along the lateraldirection L between the first sidewall 52 and the second sidewall 54.The motor 72 may be connected to the blade assembly 70, such as throughthe housing 74 to the blades via a shaft. Operation of the motor 72 mayrotate the blades, thus generally operating the blower fan 42. Further,in exemplary embodiments, motor 72 may be disposed exterior to theheater housing 46. Accordingly, the shaft may for example extend throughone of the sidewalls 52, 54 to connect the motor 72 and blade assembly70.

Heating unit 44 in exemplary embodiments includes one or more heaterbanks 80. Each heater bank 80 may be individually powered, separatelyfrom other heater banks 80, to provide heat. In exemplary embodiments,three heater banks 80 may be utilized. Further, each heater bank 80 mayin some embodiments have a different rated power level. For example insome embodiments, a heating unit 44 may include a low power heater bank,a medium power heater bank, and a high power heater bank. In somespecific embodiment, heating unit 44 include a 1000 Watt bank 80, a 1400Watt bank 80, and a 2400 Watt bank 80. Each heater bank 80 may furtherinclude at least one heater coil or coil pass 82, such as in exemplaryembodiments two heater coils or coil passes 82. As show, in exemplaryembodiments multiple heater banks 80 may be stacked vertically, and thecoils 82 of a heater bank 80 may be arranged side-by-side. Accordingly,in exemplary embodiments wherein each heater bank 80 has two heatercoils 82 the coils 82 may be arranged in two columns and three rows asshown.

The operation of air conditioner unit 10 including blower fan 42, heaterbanks 80, heating coils 82 thereof, and other suitable components may becontrolled by a processing device such as a controller 85. Controller 85may be in communication (via for example a suitable wired or wirelessconnection) to such components of the air conditioner unit 10. By way ofexample, the controller 85 may include a memory and one or moreprocessing devices such as microprocessors, CPUs or the like, such asgeneral or special purpose microprocessors operable to executeprogramming instructions or micro-control code associated with operationof unit 10. The memory may represent random access memory such as DRAM,or read only memory such as ROM or FLASH. In one embodiment, theprocessor executes programming instructions stored in memory. The memorymay be a separate component from the processor or may be includedonboard within the processor.

Unit 10 may additionally include a control panel 87 and one or more userinputs 89, which may be included in control panel 87. The user inputs 89may be in communication with the controller 85. A user of the unit 10may interact with the user inputs 89 to operate the unit 10, and usercommands may be transmitted between the user inputs 89 and controller 85to facilitate operation of the unit 10 based on such user commands. Adisplay 88 may additionally be provided in the control panel 87, and maybe in communication with the controller 85. Display 88 may, for examplebe a touchscreen or other text-readable display screen, or alternativelymay simply be a light that can be activated and deactivated as requiredto provide an indication of, for example, an event or setting for theunit.

A power source 90 may supply power to the unit 10 generally, andspecifically to the controller 85, fan 42 (and motor 72 thereof) andheater banks 80. Power source 90 may generally be any suitableelectrical power source, such as a power cable that is connected to thevarious components of the unit 10. Power source 90 may interact with apower supply 92, such as the electrical grid, via for example a poweroutlet and suitable wiring as is generally understood. The power source90 may thus generally provide the electrical communication between thepower supply 92 and the unit 10 generally and components thereof.

Unit 10 may additionally include a temperature sensor 95, which may bedisposed within the interior 51 of housing 46 to measure, for example,temperatures during a heating mode when the heating unit 44 generally isactive and/or temperature during a cooling mode. Sensor 95 may be incommunication with the controller 85, and may provide such temperaturereadings to the controller 85.

As discussed, improved methods and apparatus for reducing or preventingoverheating of air conditioner units 10 during operation thereof wouldbe advantageous. Accordingly, the present disclosure is further directedto methods for operating air conditioner units 10. It should further beunderstood that, in exemplary embodiments, a controller 85 in accordancewith the present disclosure may be operable to perform the variousmethods steps as disclosed herein. Controller 85 may advantageously bein communication with, for example, the motor 72 and the heater banks 80to facilitate such operation.

A method 200 may thus include, for example, the step 210 of determiningan operational mode 212 for the air conditioner unit 10. The unit 10may, for example, be operated in a cooling mode or a heating mode, as isgenerally understood. If it is determined that the air conditioner unit10 is operating in a cooling mode, present operation of the unit 10 maysimply be continued, with no further action taken with respect topresently disclosed methods. The continuation of present operation inaccordance with the present disclosure is generally continuance ofoperation of the unit 10 in accordance with the present settings, withno adjustments in accordance with the present method. If it isdetermined that the air conditioner unit 10 is operating in a heatingmode, further steps may be taken in accordance with the presentdisclosure.

Method 200 may further include, for example, the step 220 of determiningan operational state 222 of each heater bank 80 of the air conditionerunit 10. In some embodiments, such as when step 210 is first performed,the step 220 may only occur when the operational mode 212 is a heatingmode, as discussed above. The operational state 222 may, for example, beactive or inactive. In an active state, the heater bank 80 is operatingto provide heat, and in the inactive state, the heater bank 80 is notoperating to provide heat.

In some cases, at least one of the plurality of heater banks 80 may beinactive. In some embodiments, method 200 may thus further include, forexample, the step 225 of continuing present operation of the unit 10when the operation state 222 of at least one heater bank 80 is inactive.

In other cases, the operational state 222 of each and every heater bank80 may be active. Method 200 may thus further include, for example, thestep 230 of determining a speed 232 of the blower fan 42. In someembodiments, such step 230 may only occur when the operational state ofeach heater bank 80 is active. Blower fan 42 may be operable at avariety of speeds 232, such as a low speed, one or more optionalintermediate speeds, and a high speed.

In some embodiments, suitable components such as speed sensors,rotational frequency sensors, etc. may be utilized to determine thespeed 232 of the blower fan 42. In other embodiments, step 230 mayinclude the step 235 of determining a speed setting 237. As discussedabove, the speed setting 237 for the fan 42 may, for example, be a lowspeed setting or a high speed setting or, optionally, one or moreintermediate speed settings. The speed setting 237 may be selected by auser, and associated signals may be transmitted to the fan 42 (andspecifically the motor 72 thereof) to operate the fan 42 at a speed 232associated with that setting 237. Accordingly, when the speed setting237 is a low speed setting, the speed 232 is a low speed. When the speedsetting 237 is a high speed setting, the speed 232 is a high speed. Whenthe speed setting 237 is an intermediate speed setting, the speed 232 isan intermediate speed. As such, by determining the speed setting 237,the speed 232 may additionally be determined.

In further embodiments, the speed setting 237 may be an automaticsetting. The automatic setting is generally a setting that allows thespeed 232 to be determined and adjusted based on other variable duringoperation, such as temperature differentials. Accordingly, in someembodiments, the step 230 of determining the speed 232 of the blower fan42 may include the step 240 of comparing an actual temperaturedifferential 242 to a differential threshold 244. In some embodiments,step 240 may occur only when the speed setting 237 is the automaticsetting. The actual temperature differential 242 may be a difference inan actual temperature as measured by, for example, temperature sensor95, and a desired temperature that is for example set by a user andsaved in the controller 85. The differential threshold 244 is apredetermined temperature difference that is programmed into thecontroller 85. For example, if the actual temperature is less than orequal to the differential threshold, the fan 42 may be operated at onespeed, and if the actual temperature is greater than the differentialthreshold 244, the fan 42 may be operated at a different speed. In someembodiments, for example, the speed 232 is a low speed when the actualtemperature differential 242 is less than or equal to the differentialthreshold 244 and the speed 232 is a high speed when the actualtemperature differential 242 is greater than the differential threshold244.

Accordingly, the speed 232 of the fan 42 may be determined in accordancewith the present disclosure. In some cases, the speed 232 may be a highspeed or an intermediate speed. In some embodiments, method 200 may thusfurther include, for example, the step 245 of continuing presentoperation of the unit 10 when the speed 232 is a high speed orintermediate speed.

In other cases, the speed 232 may be a low speed. Method 200 may thusfurther include, for example, the step 250 of comparing a blower faninput voltage 252 to a blower fan voltage threshold value 254. In someembodiments, such step 250 may only occur when the speed 232 is a lowspeed. The blower fan input voltage 252 is the measured input voltage tothe blower fan 42, such as to the motor 72 thereof. For example, avoltage sensor 100 may be connected to the motor 72 or to electricalwiring upstream of the motor 72 to measure such input voltage. Thevoltage sensor 100 may, for example, be in communication with thecontroller 85, and may transmit such input voltage 252 data to thecontroller 85. The blower fan voltage threshold value 254 is apredetermined voltage value that is programmed into the controller 85.

It should be noted that, in exemplary embodiments, the blower fan 42 maybe operated, such as by the controller 85, at a generally constant inputvoltage when operating at one or more speeds 232. For example, blowerfan 42 may operate at one generally constant input voltage whenoperating at the low speed. Blower fan 42 may operate at other generallyconstant input voltage when operating at the high speed or anintermediate speed. Accordingly, when the blower fan 42 is set to aparticular speed, such as the low speed, the input voltage to the motor72 may be generally constant despite changes in one or more othervariables during operation, such as for example, input air flow to theblower fan 42.

Further, because the blower fan 42 is operating at a generally constantrotational frequency when operating at a particular speed, such as thelow speed, the input voltage 252 may be adjusted in response to changesin input air flow. The controller 85 may, for example, be operable tocause such changes in input voltage 252. For example, if a blockage orsome other event occurs such that the input air flow to or output airfrom the unit 10 generally or the fan 42 specifically is reduced, lesstorque may be required for the blower fan 42 to operate at a generallyconstant rotational frequency for a particular speed. The input voltage252 may thus be adjusted in accordance with the present disclosure. Forexample, the input voltage 252 may be reduced in such event such thatthe generally constant rotational frequency is maintained for aparticular speed.

Further, such information can be utilized when comparing the blower faninput voltage 252 to the blower fan voltage threshold value 254 suchthat blockages can be recognized and the unit 10 can respondappropriately. For example, in some cases, the blower fan input voltage252 may be greater than or equal to the blower fan voltage thresholdvalue 254. In these embodiments, method 200 may thus further include,for example, the step 255 of continuing present operation of the unit 10when the blower fan input voltage 252 is greater than or equal to theblower fan voltage threshold value 254. In other cases, the blower faninput voltage 252 may be less than the blower fan voltage thresholdvalue 254. Method 200 may thus further include, for example, the step260 of deactivating one of the plurality of heater banks 80. In someembodiments, such step 260 may only occur when the blower fan inputvoltage 252 is less than the blower fan voltage threshold value 254.Advantageously, the risk of overheating of the unit 10 is thus reducedor eliminated by deactivating one of the plurality of heater banks 80when it is detected that all heater banks 80 are active, the fan speed232 is low, and the blower fan input voltage 252 is less than the blowerfan voltage threshold value 254, thus indicating the presence orpotential presence of a blockage.

In exemplary embodiments, the low power heater bank 80 is deactivatedwhen the blower fan input voltage 252 is less than the blower fanvoltage threshold value 254. Alternatively, however, the medium powerheater bank 80, high power heater bank 80, or any other suitable heaterbank(s) 80 may be deactivated when the blower fan input voltage 252 isless than the blower fan voltage threshold value 254.

In some embodiments, method 200 may additionally provide an indicationthat a blockage or potential blockage has been detected. For example,method 200 may further include the step 270 of transmitting a low airflow signal 272 when the blower fan input voltage 252 is less than theblower fan voltage threshold value 254. Such signal 272 may, forexample, be transmitted by the controller 85 to, for example, thedisplay 88. Such transmission, and resulting output provided by thedisplay 88, may advantageously provide an indication to a user that alow air flow event, potentially due to a blockage, has occurred.

It should be noted that, in exemplary embodiments, the deactivatedheater bank 80 may be re-activated when, for example, the speed 232 ischanged from a low speed to another speed, such as a high speed, or whena blockage is removed from the inlet or outlet air flow.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A method for operating an air conditioner unithaving a selectable high and low blower speed, the low speed beingrelatively less than the high speed, the method comprising: initiating apresent operation; determining an operational state of each heater bankof a plurality of heater banks of the air conditioner unit, theplurality of heater banks comprising a low power heater bank and a highpower heater bank; determining an operational rotation speed of a blowerfan of the air conditioner unit when the operational state of everyheater bank is active during the present operation; comparing a blowerfan input voltage to a voltage threshold value when the determinedoperational rotation speed is the low speed; deactivating only the lowpower heater bank when the blower fan input voltage is less than thevoltage threshold value; and continuing the present operation inresponse to the step of deactivating the low power heater bank.
 2. Themethod of claim 1, further comprising continuing the present operationwhen the determined operational rotation speed is the high speed andevery heater bank is active.
 3. The method of claim 1, furthercomprising determining an operational mode for the air conditioner unit,and wherein the step of determining an operational state of each heaterbank occurs when the operational mode is a heating mode.
 4. The methodof claim 1, wherein the step of determining the operational rotationspeed of the blower fan comprises determining a speed setting.
 5. Themethod of claim 4, wherein the determined operational rotation speed isthe low speed when the speed setting is a low speed setting and thedetermined operational rotation speed is the high speed when the speedsetting is a high speed setting.
 6. The method of claim 4, wherein thestep of determining the operational rotation speed of the blower fancomprises comparing an actual temperature differential to a differentialthreshold when the speed setting is an automatic setting, and whereinthe determined operational rotation speed is the low speed when theactual temperature differential is less than or equal to thedifferential threshold and the determined operational rotation speed isthe high speed when the actual temperature differential is greater thanthe differential threshold.
 7. The method of claim 1, further comprisingtransmitting a low air flow signal when the blower fan input thresholdis less than the voltage threshold value.
 8. The method of claim 1,wherein the blower fan operates at a constant rotational frequency whenoperating at the low speed.
 9. The method of claim 1, wherein theplurality of heater banks further comprises a medium power heater bank.10. An air conditioner unit having a selectable high and low blowerspeed, the low speed being relatively less than the high speed, the airconditioner unit comprising: a blower fan, the blower fan comprising ablade assembly and a motor connected to the blade assembly; a heatingunit, the heating unit comprising a plurality of heater banks, theplurality of heater banks comprising a low power heater bank and a highpower heater bank; a power source in electrical communication with theblower fan motor and the plurality of heater banks; and a controller inoperable communication with the motor and the plurality of heater banks,the controller operable for: initiating a present operation; determiningan operational state of each heater bank; determining an operationalrotation speed of the blower fan when the operational state of everyheater bank is active during the present operation; comparing a blowerfan input voltage to a voltage threshold value when the determinedoperational rotation speed is the low speed; deactivating only the lowpower heater bank when the blower fan input voltage is less than thevoltage threshold value; and continuing the present operation inresponse to deactivating the low power heater bank.
 11. The airconditioner unit of claim 10, wherein the controller is further operablefor continuing the present operation when the determined operationalrotation speed is the high speed and every heater bank is active. 12.The air conditioner unit of claim 10, wherein the controller is furtheroperable for determining an operational mode for the air conditionerunit, and wherein determining an operational state of each heater bankoccurs when the operational mode is a heating mode.
 13. The airconditioner unit of claim 10, wherein determining the operationalrotation speed of the blower fan comprises determining a speed setting.14. The air conditioner unit of claim 13, wherein determining theoperational rotation speed of the blower fan comprises comparing anactual temperature differential to a differential threshold when thespeed setting is an automatic setting, and wherein the determinedoperational rotation speed is the low speed when the actual temperaturedifferential is less than or equal to the differential threshold and thedetermined operational rotation speed is the high speed when the actualtemperature differential is greater than the differential threshold. 15.The air conditioner unit of claim 10, wherein the controller is furtheroperable for transmitting a low air flow signal when the blower faninput threshold is less than the voltage threshold value.
 16. The airconditioner unit of claim 10, wherein the blower fan operates at aconstant input voltage when operating at the low speed.
 17. The airconditioner unit of claim 10, wherein the plurality of heater banksfurther comprises a medium power heater bank.
 18. A method for operatingan air conditioner unit having a selectable high and low blower speed,the low speed being relatively less than the high speed, the methodcomprising: initiating a present operation; determining an operationalstate of each heater bank of a plurality of heater banks of the airconditioner unit during the present operation; determining anoperational rotation speed of a blower fan of the air conditioner unitwhen the operational state of every heater bank is determined to beactive; comparing a blower fan input voltage to a voltage thresholdvalue in response to the step of determining an operational rotationspeed when the determined operational rotation speed is the low speed;deactivating only one of the plurality of heater banks when the blowerfan input voltage is less than the voltage threshold value; continuingthe present operation in response to the step of deactivating only oneof the plurality of heater banks; and continuing the present operationin response to the step of determining an operational state of eachheater bank when the determined operational rotation speed is the highspeed and every heater bank is active.